Several other users have reported the same problem since the upgrade. Clearing out old cookies has solved the problem in every case. In IE, just go to Tools -> Internet Options, then hit "Delete cookies". If you don't want to wipe all your cookies, you can search your cookie folder for any TalkBass cookies and delete them individually.

Once that's done, you'll have to log in of course, but you should stay logged in. Let me know if this works -